The present invention relates generally to copolymers containing components of polyphosphazene as part of the copolymer backbone or as a sidegroup.
Polyphosphazene-containing polymers have been used in applications in the field of biomedical materials, conductive polymers, and elastomers. Polyphosphazene-containing polymers are also of general interest because of their capability to combine with another polymer, either organic or inorganic, incorporating the properties and advantages of the two polymer components without sacrificing the overall chemical, physical, and mechanical properties of each component. For instance, the synthesis of hybrid block and graft copolymers of polyphosphazenes and polystyrene is a way to combine the attributes of both polymers and generate new properties. Many of the valuable properties of the respective phosphazene and styrene homopolymers can be combined without sacrificing the overall solid state or solution properties of both polystyrene and polyphosphazene polymers. For example, block or graft copolymers of polyphosphazenes and polystyrene have improved fire resistance compared to polystyrene alone.
Thus far, efforts to combine polyphosphazenes with another polymer backbone to form a copolymer to take advantage of the attributes of each component has had only very limited success. For instance, the incorporation of organosiloxanes and polyphosphazenes into one material, although successful, has not resulted in linear phosphazene-siloxane block copolymers combining the attributes of the two inorganic backbone systems. Moreover, until recently, the preparation of block copolymers containing polyphosphazenes, has been limited to species with two phosphazene components. The synthesis of telechelic polyphosphazenes which may be used to couple with preformed organic polymers has proved to be difficult.
Traditionally, block copolymers have been synthesized via sequential polymerization of different monomers. However, the limited number of compatible initiating monomers places limits on the number of copolymers that can be synthesized by the sequential method. It therefore would be advantageous to develop an approach that can readily incorporate polyphosphazenes along with other polymeric systems to yield copolymers having the advantages of both polymeric components.
Therefore, it is an object of the present invention to provide methods for the synthesis of telechelic polyphosphazenes for the purposes of making polyphosphazene-containing organic-inorganic copolymers.
It is another object of the present invention to provide synthetic methods for the preparation of polymeric compositions that contain a polyphosphazene component.
It is another object of the present invention to provide methods for combining a polyphosphazene backbone with another polymeric backbone to form new copolymers.
It is a further object of the present invention to provide a method to modify polyphosphazenes with various functional groups to provide polyphosphazene polymers with different chemical and physical properties.
It is still another object of the present invention to provide methods to prepare polyphosphazene compositions which are readily incorporated into other polymeric compositions.
Compositions of polyphosphazene-containing polymers and methods of preparation thereof are provided. The compositions may contain either organic or inorganic components. A large variety of organic side groups can be further incorporated as sidegroups on the polyphosphazene to tailor the properties of these materials. Exemplary polymeric compositions which can be incorporated include polystyrene, polysiloxanes, polynorbornene, poly(methyl methacrylate), polyolefins, polydienes, and polyethylenes.
Methods for the preparation of compositions of polyphosphazene-containing polymers generally involve the steps of generation of a poly(dihalophosphazene) species, attachment of a functional group to the resultant polyphosphazene compound, and coupling the functionalized polyphosphazene with a corresponding organic or inorganic polymer or polymerizing the functionalized polyphosphazene with corresponding organic molecules. A large number of polyphosphazene-containing polymers can be prepared accordingly.
The polyphosphazene compositions disclosed are useful as elastomers, optical materials, electrically conductive materials, biomedical materials, compatibilizing agents, surfactants, additives for coatings, and as flame retardants.